Seat device for vehicle

ABSTRACT

A vehicle seat apparatus includes a seat, an actuator, and a controller in which a posture control unit exercises a seat posture control over the actuator based on a lateral acceleration and a steering velocity, to change an orientation of at least a portion of the seat. The posture control unit is configured to activate the seat posture control when a magnitude of the lateral acceleration becomes greater than a first acceleration threshold value, as well as to activate the seat posture control on conditions that the steering velocity has a magnitude greater than a steering velocity threshold value and when the magnitude of the lateral acceleration becomes greater than a second acceleration threshold value of which a magnitude is smaller than the first acceleration threshold value and a direction is laterally opposite to a direction of the steering velocity.

TECHNICAL FIELD

The present invention relates to a vehicle seat apparatus having acapability of changing an orientation of at least a portion of a seatback in accordance with a state of a vehicle making a turn.

BACKGROUND ART

A car seat apparatus configured such that when a vehicle turns, a seatback plate portion is swiveled to orient toward a turning direction soas not to allow the feature of holding an occupant to be impaired due toa lateral acceleration produced in a direction reverse to the turningdirection is hitherto known in the art (e.g., Patent Document 1).According to the invention disclosed in the Patent Document 1, a controlexercised is such that the lateral acceleration to be imposed on the caris estimated by computation, and when the lateral acceleration exceeds apredetermined threshold value, the orientation of the seat back plateportion is changed (such a control will be hereinafter referred to as“seat posture control”).

CITATION LIST Patent Literature

Patent Document 1: JP 2013-049357 A

SUMMARY OF INVENTION

However, in cases of abrupt steering operations, such as a sharp-turnsteering operation where the steering wheel turned to the right isturned reversely to the left, the lateral acceleration increasesabruptly, and thus if the actuation for the seat posture control isstarted on condition that the lateral acceleration exceeds apredetermined threshold value as proposed in Patent Document 1, theactuation for the seat posture control would disadvantageously becompleted too late to achieve a good hold of the occupant.

Against this backdrop, the present invention has been made, and anobject pursued herein is to provide a vehicle seat apparatus in which agood hold of an occupant can be achieved.

The present invention proposed in an attempt to achieve theaforementioned object provides a vehicle seat apparatus comprising: aseat including a seat cushion and a seat back; an actuator capable ofchanging an orientation of at least a portion of the seat; and acontroller configured to control the actuator, wherein the controllerincludes: a lateral acceleration acquisition unit configured to acquirea lateral acceleration; a steering velocity acquisition unit configuredto acquire a steering velocity; and a posture control unit configured toexercise a seat posture control over the actuator based on the lateralacceleration acquired by the lateral acceleration acquisition unit andthe steering velocity acquired by the steering velocity acquisitionunit, to change the orientation of the at least a portion of the seat.The posture control unit is configured: to activate the seat posturecontrol when a magnitude of the lateral acceleration becomes greaterthan a first acceleration threshold value, as well as to activate theseat posture control when an increase of the lateral acceleration due toa sharp-turn steering operation is predicted.

In general, quick steering operation of a steering wheel of a vehiclemay result with high probability in subsequent generation of a greatmagnitude of the lateral acceleration in a direction opposite to thesteering direction of the steering wheel, that is, the turningdirection. Therefore, the seat posture control is also activated when anincrease of the lateral acceleration due to a sharp-turn steeringoperation is predicted based on the steering velocity, and thus theactuation according to the seat posture control can be started earlier,so that a good hold of an occupant can be achieved.

In the apparatus described above, the posture control unit may beconfigured to activate the seat posture control on condition that thesteering velocity has a magnitude greater than a steering velocitythreshold value and when the magnitude of the lateral accelerationbecomes greater than a second acceleration threshold value which issmaller than the first acceleration threshold value and of which adirection is laterally opposite to a direction of the steering velocity.

If the magnitude of the steering velocity is greater than a steeringvelocity threshold value and the magnitude of the lateral accelerationis smaller than the first acceleration threshold value but becomesgreater than the second acceleration threshold value which is smallerthan the first acceleration threshold value and of which a direction islaterally opposite to a direction of the steering velocity, an increaseof the lateral acceleration due to a sharp-turn steering operation maybe predicted. Therefore, the actuation for the seat posture control thusstarted under this condition means that the actuation for the seatposture control can be started before the magnitude of the lateralacceleration becomes greater than the first acceleration thresholdvalue; consequently, a good hold of an occupant can be achieved.

In the apparatus described above, the second acceleration thresholdvalue may be smaller than a half of the first acceleration thresholdvalue. With this feature, the seat posture control can be started in atimely fashion, so that a good hold can be achieved.

The aforementioned steering velocity threshold value may preferably bein a range of 100 to 150 deg/s. With this feature, the seat posturecontrol can be started in a timely fashion, so that a good hold can beachieved.

Moreover, the posture control unit may be configured to bring the seatposture control to an end when the magnitude of the lateral accelerationbecomes smaller than a reset threshold value during the seat posturecontrol.

Furthermore, if a magnitude of the second acceleration threshold valueis set to be smaller than a magnitude of the reset threshold value, theseat posture control can be started in a timely fashion, so that a goodhold can be achieved.

The steering velocity threshold value may preferably be configured to bevariable through an operation of a user. With this configuration, a goodfeel of being held in the seat as preferred by the user can be realizedthrough a change of the steering velocity threshold value according tothe preference of the user. Also, in this embodiment, the controller mayinclude a nonvolatile memory in which the steering velocity thresholdvalue is storable, so that user's settings can be retained therein.

In the apparatus described above, the seat back may include a centralportion for allowing a back of an occupant to rest thereagainst, andside portions disposed at left and right sides of the central portionand jutting frontward farther than the central portion. In thisembodiment, the actuator may be configured to actuate the centralportion, and/or may be configured to actuate the side portions.

In the apparatus describe above, the actuator may be configured toactuate an entire body of the seat back, or may be configured to actuatean entire body of the seat.

In the apparatus described above, the seat back may include a seat backframe and a seat back pad, and a pressure-receiving member may beprovided which is supported by the seat back frame at a positionrearward of the seat back pad and configured to be movable rearward by arearward motion load acted on the seat back from an occupant. In thisembodiment, the actuator may be configured to actuate thepressure-receiving member.

The lateral acceleration acquisition unit may preferably be configuredto acquire the lateral acceleration by computation based on a vehiclevelocity and a steering angle.

In an alternative embodiment where the lateral acceleration is acquiredfrom a lateral acceleration sensor, the acquired value of the lateralacceleration can sensitively vary depending on the inclination of thevehicle, or ruts on the road, or the like; in this embodiment, however,the lateral acceleration acquired by computation based on the vehiclevelocity and the steering angle is used, and thus any sensitivevariation of the lateral acceleration can be restricted and a stablecontrol can be exercised with a simple configuration.

Additionally, in this embodiment, the lateral acceleration acquisitionunit may be configured to compute the lateral acceleration GC by:

R=(1+AV ²)/(L/φ)

GC=V ² /R

where A: Stability factor, a vehicle-specific constant

L: Whoelbase of a vehicle

φ: Steering angle

R: Turning radius.

In the apparatus described above, the lateral acceleration acquisitionunit may be configured to acquire values of the lateral accelerationfrom a lateral acceleration sensor, or alternatively, may be configuredto acquire values of the lateral acceleration from an electronic controlunit provided in a vehicle.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a car seat apparatus as an example of avehicle seat apparatus according to one embodiment.

FIG. 2 is a perspective view of a seat frame incorporated in the carseat apparatus.

FIG. 3 is an enlarged perspective view of a posture control mechanism.

FIG. 4 includes plan views showing operations of the posture controlmechanism, in (a) no-turn state, (b) right-turn state, and (c) left-turnstate.

FIG. 5 is a block diagram for explaining a configuration of acontroller.

FIG. 6 is a flowchart showing a preliminary process of a seat posturecontrol.

FIG. 7 is a flowchart showing process steps of determination forstarting actuation for the seat posture control and execution of theseat posture control during a right-turn operation.

FIG. 8 is a flowchart showing process steps of determination forstarting actuation for the seat posture control and execution of theseat posture control during a left-turn operation.

FIG. 9 is a timing chart showing a steering velocity, a lateralacceleration and a control flag, during a travel of a car.

FIG. 10 is an exploded perspective view of a seat apparatus according toa first modified embodiment.

FIG. 11 is an exploded perspective view of a seat apparatus according toa second modified embodiment.

FIG. 12 is a block diagram of a controller in a seat apparatus accordingto a third modified embodiment.

FIG. 13 is a block diagram of a controller in a seat apparatus accordingto a fourth modified embodiment.

DESCRIPTION OF EMBODIMENTS

Hereafter, one embodiment of the present invention will be described indetail with reference made to the drawings where appropriate. In thefollowing description, a mechanical setup of a car seat as one exampleof a vehicle seat apparatus will be discussed at the outset, and then aconfiguration for controlling the posture control mechanism will bediscussed.

<Mechanical Setup of Car Seat>

As shown in FIG. 1, a car seat apparatus 1 is a seat apparatus for usein a driver's seat of an automobile, and mainly comprises a seat S whichincludes a seat cushion S1, a seat back S2 and a headrest S3. The seatback S2 includes a central portion S21 for allowing a back of anoccupant to rest thereagainst, and side portions S22 disposed at leftand right sides of the central portion S21 and jutting frontward fartherthan the central portion S21. It is to be understood that the car seatapparatus 1 may be installed not only in the driver's seat, but also inthe passenger seat next to the driver's seat, a rear seat, or any otherseat locations.

The seat cushion S1 and the seat back S2 are configured to incorporate aseat frame F as shown in FIG. 2. The seat frame F mainly includes a seatcushion frame F1 constituting a frame of the seat cushion S1, and a seatback frame F2 constituting a frame of the seat back S2. The seat cushionS1 is formed by upholstering the seat cushion frame F1 with a seatcushion pad made of a cushiony material such as urethane foam, and anouter covering material made of synthetic leather, fabric or the like.The seat back S2 is formed by upholstering the seat back frame F2 with aseat back pad made of a cushiony material, and an outer coveringmaterial made of synthetic leather, fabric or the like.

The seat back frame F2 has a lower portion thereof pivotally connectedvia a reclining mechanism RL to a rear portion of the seat cushion frameF1. This allows the seat back S2 to be tilted frontward and rearwardrelative to the seat cushion S1.

It is to be noted that the directions in this description, i.e.,front/rear (frontward/rearward), left/right (leftward/rightward;lateral) and upper/lower (upward/downward), are designated withreference to an occupant seated on the car seat apparatus 1 in itsunreclined position such that the seat back S2 is not tilted down bymeans of the reclining mechanism RL.

The seat back frame F2 is configured to mainly include an upper frame10, left and right side frames 20 and a lower frame 30, and formed inthe shape of a frame with the upper frame 10, the left and right sideframes 20 and the lower frame 30 welded or otherwise joined together inone piece. At an inside of this frame-like seat back frame F2, apressure-receiving member 40 configured to support a back of an occupantand a posture control mechanism 50 configured to change an orientationof the pressure-receiving member 40 to the left and to the right arearranged.

The pressure-receiving member 40 is an elastically deformable plate-likemember made of plastic or the like, and disposed rearward of the seatback pad between the left and right side frames 20. To be more specific,the pressure-receiving member 40 includes a pressure-receiving portion40A for supporting the back of an occupant through the seat back pad,and support portions 41 protruding from left and right end portions ofan upper portion of the pressure-receiving portion 40A inlaterally-outward-and-frontward-directions. The pressure-receivingportion 40A is located in a position rearward of the central portion S21of the seat back S2, while the support portions 41 are located inpositions rearward of the side portions S22. The support portions 41serve to support an upper portion of the upper body from left and rightside directions.

The pressure-receiving member 40 is engaged with, and supported by anupper connecting wire W1 and a lower connecting wire W2 which aredisposed rearward of the pressure-receiving member 40. The upperconnecting wire W1 has its both end portions engaged with and supportedby the posture control mechanisms 50, and the lower connecting wire W2has its both end portions engaged with and supported by swing motionmechanisms 21 provided at laterally inner sides of the left and rightside frames 20. In this way, the pressure-receiving member 40 isconfigured to be movable rearward by a rearward motion load acted on theseat back from an occupant.

The posture control mechanism 50 is disposed at each of left and rightsides of the pressure-receiving member 40, and configured to be capableof changing an orientation of the pressure-receiving member 40 to theleft or to the right by pushing frontward and moving the left sideportion or the right side portion of the pressure-receiving member 40under control of the controller 100 (see FIG. 5).

As shown in FIG. 3, the posture control mechanism 50 mainly includes anactuator 51, a holding bracket 52, a first link member 53, a second linkmember 54, and a torsion spring 55 as a biasing member.

The actuator 51 is a source of driving power for causing the first linkmember 53 and the second link member 54 to rotate, and configured toinclude a stepping motor 51A which can be rotated in normal and reversedirections, a gear box 51B, and an output shaft 51C, wherein the outputshaft 51C is disposed to extend along an upward-downward direction. Theactuator 51 is fixed to the side frame 20 by the holding bracket 52. Thedriving power from the stepping motor 51A is transmitted with a speedreduced in the gear box 51B, to the output shaft 51C, to cause theoutput shaft 51C to rotate.

The first link member 53 is an elongated plate member, and has one endportion thereof fixed to the output shaft 51C of the actuator 51, sothat the other end portion thereof can be swung on the output shaft 51Cfrontward and rearward. On top of the first link member 53, tworestricting walls 58 for defining a range of the swinging motion of thesecond link member 54 are protrusively provided.

The second link member 54 is pivotally connected to the first linkmember 53. At a distal end portion of the second link member 54, aconnecting hole 54B with which the aforementioned end portion of theupper connecting wire W1 is pivotally engaged is formed.

The torsion spring 55 has one end thereof engaged with the first linkmember 53 and the other end thereof engaged with the second link member54, to thereby bias the second link member 54 in a clockwise directionas viewed from above with respect to the first link member 53.

In the description given herein, the right posture control mechanism 50shown in FIG. 3 has been described, and it is to be understood that theleft posture control mechanism 50 is bilaterally symmetric to the rightposture control mechanism 50.

The pressure-receiving member 40 in the no-turn state is, as shown inFIG. 4(a), disposed in a rearward position as the left and right posturecontrol mechanisms 50 are not actuated. In the right-turn state as shownin FIG. 4(b), the stepping motor 51A of the left posture controlmechanism 50 rotates in the normal direction, the first link member 53swings frontward, and the pressure-receiving member 40 is caused toorient rightward under control of the controller 100 as will bedescribed later. In the left-turn state as shown in FIG. 4(c), on theother hand, the stepping motor 51A of the right posture controlmechanism 50 rotates in the normal direction, the first link member 53swings frontward, and the pressure-receiving member 40 is caused toorient leftward under control of the controller 100. To restore theposture from the state shown in FIG. 4(b) to the state shown in FIG.4(a), the stepping motor 51A of the left posture control mechanism 50 iscaused to rotate in the reverse direction; to restore the posture fromthe state shown in FIG. 4(c) to the state shown in FIG. 4(a), thestepping motor 51A of the right posture control mechanism 50 is causedto rotate in the reverse direction. In this way, the posture controlmechanism 50 is configured to move the pressure-receiving member 40,thereby moving the central portion S21 and the side portions S22 of theseat back S2.

<Configuration for Control of Posture Control Mechanism>

As shown in FIG. 5, the controller 100 includes a lateral accelerationacquisition unit 110, a steering velocity acquisition unit 120, aposture control unit 130, a threshold setting unit 140, and a storageunit 190, in order to exercise control over the actuator 51 to regulatethe lateral orientation of the pressure-receiving member 40. Thecontroller 100 includes a CPU (central processing unit), a ROM (readonly memory), a RAM (random access memory) and other modules which arenot illustrated in the drawings, and implements the respective units byloading relevant programs pre-stored in the storage unit 190 andexecuting them.

The lateral acceleration acquisition unit 110 is means for acquiring alateral acceleration imparted to a car, and is configured in the presentembodiment to work out the lateral acceleration GC by computation basedon a wheel velocity acquired from a wheel velocity sensor 91 and asteering angle acquired from a steering angle sensor 92. To be morespecific, the lateral acceleration GC may be computed by the followingequations with a car body velocity V determined from the wheel velocityby a known method and using a stability factor A as a constant specificto the car, a whoel base L of the car, a steering angle φ, and a turningradius R:

R=(1+AV ²)/(L/φ)

GC=V ² /R

The steering velocity acquisition unit 120 is means for acquiring asteering velocity, and is configured to compute a steering velocity SVby differentiation (e.g., by finding the differential between thepresent measurement and the preceding measurement) of the steering angleacquired from the steering angle sensor 92.

It is to be understood that, in the present embodiment, the steeringangle φ and the steering velocity SV are taken from the angle andvelocity of the steering operation of the steering wheel, but may betaken from the angle and velocity of the turning motion of the carwheel(s) if the constants are changed. It is also to be understood thatthe lateral accelerations GC and the steering velocities SV directed tothe right and to the left are represented herein, respectively, bypositive and negative values.

The posture control unit 130 is means for exercising a seat posturecontrol over the actuator 51 based on the lateral acceleration GCacquired by the lateral acceleration acquisition unit 110 and thesteering velocity SV acquired by the steering velocity acquisition unit120, to orient the pressure-receiving member 40 in the turningdirection. The posture control unit 130 is configure to activate theseat posture control when a magnitude (absolute value) of the lateralacceleration GC becomes greater than a first acceleration thresholdvalue GCth1, as well as to activate the seat posture control oncondition that the steering velocity SV has a magnitude (absolute value)greater than a steering velocity threshold value SVth and when themagnitude of the lateral acceleration becomes greater than a secondacceleration threshold value GCth2 which is smaller than the firstacceleration threshold value GCth1 and of which a direction of thelateral acceleration is opposite to a direction of the steering velocitySV. In other words, the posture control unit 130 is configured to alsoactivate the seat posture control when an increase of the lateralacceleration GC due to a sharp-turn steering operation is predicted. Therespective threshold values may be determined in accordance with thecharacteristics of the car through a test driving; for a typicalpassenger car, the steering velocity threshold value SVth may preferablybe set generally in a range of 100 to 150 deg/s. The second accelerationthreshold value GCth2 may preferably be smaller than a half of the firstacceleration threshold value GCth1. With this setting, the seat posturecontrol can be started with adequate timing, and a good hold can beachieved accordingly.

Herein, it is assumed that the first acceleration threshold value GCth1itself is a positive value, and when the lateral acceleration GC shouldbe considered to assume a negative value as in the right-turn state, themagnitude of the lateral acceleration GC being greater than the firstacceleration threshold value GCth1 is represented as GC<−GCth1, andother threshold values such as the second acceleration threshold valueGCth2 and the steering velocity threshold value SVth are representedsimilarly in the same situation.

The posture control unit 130 is also configured to bring the seatposture control to an end by reversing the actuator 51, when during theseat posture control, the magnitude of the lateral acceleration GCbecomes smaller than a reset threshold value Rth. Herein, the magnitudeof the second acceleration threshold value GCth2 is smaller than themagnitude of the reset threshold value Rth. With the second accelerationthreshold value GCth2 set on this condition, the seat posture controlcan be started with adequate timing, and thus a good hold can beachieved.

The threshold setting unit 140 is means for receiving inputs from anoperation panel 93 of the car, and writing a steering velocity thresholdvalue SVth in the storage unit 190 as a set value. To be more specific,a user can operate the operation panel 93 and select a preferredmagnitude of the steering velocity threshold value SVth from options ofLarge, Medium, Small, etc. to change the steering velocity thresholdvalue SVth, so that a desired feel of holding can be set.

The storage unit 190 is a device comprising a volatile memory such as aRAM and a nonvolatile memory such as an EEPROM, and configured to storevalues acquired from the respective sensors, values computed by therespective units, and set values such as threshold values.

One example of process steps of determination of start of actuation forthe seat posture control and its execution under control of thecontroller 100 configured as described above will be described withreference to FIGS. 6 to 8. It is to be understood that flowcharts inFIGS. 6 to 8 each show a series of steps from START to END which form aniterative process to be repeated. Herein, the control flag FL is set at“0” in a no-turn state when the seat posture control is not executed, at2 when the pressure-receiving member 40 is turned to the left (i.e., inthe left-turn state), and at 1 when the pressure-receiving member 40 isturned to the right (i.e., in the right-turn state). The initial valueof the control flag FL is 0.

As shown in FIG. 6, the controller 100 is configured to acquire valuesfrom the wheel velocity sensor 91 and the steering angle sensor 92(S101), and the lateral acceleration acquisition unit 110 computes alateral acceleration GC based on the values of the wheel velocity andthe steering angle (S102). The steering velocity acquisition unit 120computes a steering velocity SV based on the steering angle (S103). Theposture control unit 130 then makes a determination as to whether tostart the seat posture control, and executes the seat posture control inaccordance with the turning direction (S200). To be more specific, if inthe right-turn state, then the process of FIG. 7 is executed, while ifin the left-turn state, then the process of FIG. 8 is executed.

In the right-turn state, as shown in FIG. 7, the posture control unit130 makes a determination as to whether the lateral acceleration GC issmaller than the first acceleration threshold value GCth1 that is anegative value (i.e., whether the magnitude of the lateral accelerationGC is greater than GCth1), and if smaller (Yes in S111), then the leftactuator 51 is caused to rotate in the normal direction (S115), and thepressure-receiving member 40 is turned to the right and the control flagis set at 1 (S116).

On the other hand, even if it is determined in step S111 that thelateral acceleration GC is not smaller than the negative firstacceleration threshold value GCth1 (No in S111), the left actuator 51 iscaused to rotate in the normal direction (S115), and thepressure-receiving member 40 is turned to the right and the control flagis set at 1 (S116) on conditions that the steering velocity SV isgreater than the steering velocity threshold value SVth (Yes in S112)and the lateral acceleration GC is smaller than the negative secondacceleration threshold value GCth2 of which the direction is laterallyopposite to the direction of the steering velocity SV (i.e., themagnitude of the lateral acceleration GC is greater than the secondacceleration threshold value GCth2) (Yes in S113). If the determinationin step S112 or step S113 results in No, as well as if the seat posturecontrol has been started, then the process goes to step S131.

Thereafter, if the control flag FL is 1 (Yes in S131), i.e., thepressure-receiving member 40 is turned to the right, then the posturecontrol unit 130 makes a determination as to whether the lateralacceleration GC is greater than the reset threshold value Rth that is anegative value (i.e., whether the magnitude of the lateral accelerationGC is smaller than the reset threshold value Rth), and if greater (Yesin S132), then the left actuator 51 is caused to rotate in the reversedirection (S133), and the pressure-receiving member 40 is restored tothe no-turn state and the control flag FL is set at 0 (S134). On theother hand, if the control flag FL is not 1 (No in S131), as well as ifthe lateral acceleration GC is not greater than the negative resetthreshold value Rth (No in S132), then the process comes to an endwithout changing the control flag FL.

In the left-turn state, as shown in FIG. 8, the posture control unit 130makes a determination as to whether the lateral acceleration GC isgreater than the first acceleration threshold value GCth1, and ifgreater (Yes in S121), then the right actuator 51 is caused to rotate inthe normal direction (S125), and the pressure-receiving member 40 isturned to the left and the control flag is set at 2 (S126).

On the other hand, even if it is determined in step S121 that thelateral acceleration GC is not greater than first acceleration thresholdvalue GCth1 (No in S121), the right actuator 51 is caused to rotate inthe normal direction (S125), and the pressure-receiving member 40 isturned to the left and the control flag is set at 2 (S126) on conditionsthat the steering velocity SV is smaller than the negative steeringvelocity threshold value SVth (i.e., the magnitude of the steeringvelocity SV is greater than the steering velocity threshold value SVth)(Yes in S122) and the lateral acceleration GC is greater than thepositive second acceleration threshold value GCth2 such that thedirection of the lateral acceleration is opposite to the direction ofthe steering velocity SV (Yes in S123). If the determination in stepS122 or step S123 results in No, as well as if the seat posture controlhas been started, then the process goes to step S141.

Thereafter, if the control flag FL is 2 (S141), then the posture controlunit 130 makes a determination as to whether the lateral acceleration GCis smaller than the reset threshold value Rth, and if smaller (Yes inS142), then the right actuator 51 is caused to rotate in the reversedirection (S143), and the pressure-receiving member 40 is restored tothe no-turn state and the control flag FL is set at 0 (S144). On theother hand, if the control flag FL is not 2 (No in S141), as well as ifthe lateral acceleration GC is not greater than the negative resetthreshold value Rth (No in S142), then the process comes to an endwithout changing the control flag FL.

According to the process as described above, for example, the car seatapparatus 1 operates as shown in FIG. 9. FIG. 9 represents the changesof the steering velocity SV, the lateral acceleration GC and the controlflag FL observed when a car makes one complete circuit of the course.

As shown in FIG. 9, when the car starts driving at a time t0 on astraight section of the course, and enters a long and fast-trackleftward-curved section a short while before a time t1, though thechange in the steering velocity SV is small, the rightward lateralacceleration GC increases and becomes greater than the firstacceleration threshold value GCth1 (at the time t1); at that time, thepressure-receiving member 40 is turned to orient to the left.Thereafter, when at a time t2, the lateral acceleration GC becomessmaller than the reset threshold value Rth, the pressure-receivingmember 40 is restored to the original position.

As the rightward-curved section starts around a time past the time t2,the driver operates the steering wheel back to the right from a time ashort while before that time t2, that is, from a location short of theend of the leftward-curved section. For this reason, around the time t2,the steering velocity SV crosses SVth. While the steering velocity SVremains greater than the steering velocity threshold value SVth,additionally, when the lateral acceleration GC becomes smaller than thenegative second acceleration threshold value GCth2 (at a time t3), thepressure-receiving member 40 is turned to orient to the right.

Next, at a time t5, when the lateral acceleration becomes greater thanthe negative threshold value Rth, the pressure-receiving member 40 isrestored to the original position. As the leftward-curved section startsaround a time past the time t5, the driver operates the steering wheelback to the left from a time short while before that time t5, that is,from a location short of the end of the rightward-curved section. Forthis reason, around the time t5, the steering velocity SV crosses thenegative steering velocity threshold value SVth to the negative side.While the steering velocity SV remains at the negative side of thenegative SVth, additionally, when the lateral acceleration GC becomesgreater than the second acceleration threshold value GCth2 (at a timet6), the pressure-receiving member 40 is turned to orient to the left.

Similarly, from a time t7 to a time t8, and from a time t9 to a timet10, the sharp-turn steering operation from the left to the right andthe sharp-turn steering operation from the right to the left areperformed, respectively, and thus the pressure-receiving member 40 isrestored to the original position at the time t7, turned to orient tothe right at the time t8, restored to the original position at the timet9, and turned to orient to the left at the time t10.

Lastly, when the car drives from a leftward-curved section to a straightsection of the course, the steering wheel is operated back to theoriginal position, and thus the steering velocity SV becomes greater tothe right, and the lateral acceleration GC does not become greater tothe left. Accordingly, at a time t11, the pressure-receiving member 40is restored to the original position, but afterward not turned to orientto the right.

In the prior art, the actuation for the seat posture control is startedonly after the lateral acceleration GC crosses a predeterminedacceleration (corresponding to the first acceleration threshold valueGCth1), and thus the first sharp-turn steering operation results instart of the actuation for the seat posture control at the time t4;however, in the present embodiment, based on the quick steering velocitySV due to the sharp-turn steering operation, subsequent generation of alarge lateral acceleration GC is predicted, so that the actuation forthe seat posture control can be started at the time t3. Therefore, theactuation for the seat posture control can be started earlier than theprior-art configuration by an amount of time indicated by character D inFIG. 9, so that the occupant can be held adequately.

Moreover, the conditions imposed hereon relates not only to the steeringvelocity SV but also to the lateral acceleration GC of which themagnitude becomes greater than the second acceleration threshold valueGCth2 such that a direction of the lateral acceleration GC is laterallyopposite to a direction of the steering velocity SV; therefore, even ifthe steering velocity SV temporarily becomes great when the car drivesfrom a curved section to a straight section of the course, the seatposture control will never be activated.

As described above, with the car seat apparatus 1 according to thepresent invention, in cases of abrupt steering operations, such as asharp-turn steering operation, the actuation according to the seatposture control can be started earlier, so that a good hold of anoccupant can be achieved.

Moreover, since the car seat apparatus 1 is configured such that thesteering velocity threshold value SVth is variable through an operationof a user, a feel of being held in the seat as preferred by the user canbe realized.

Furthermore, since in the car seat apparatus 1, the lateral accelerationacquisition unit 110 is configured to acquire a lateral acceleration bycomputation based on the wheel velocity and the steering angle, a stablecontrol can be exercised without undergoing a sensitive change of thelateral acceleration with a simple configuration.

Although the embodiment of the present invention has been describedabove, the present invention is not limited to the above-describedembodiment, and can be implemented with any appropriate modificationsmade thereto.

For example, the above-described embodiment is configured to cause thepressure-receiving member 40 disposed in the seat back S2 shown in FIG.1 at a position rearward of the central portion S21 (for allowing a backof an occupant to rest thereagainst) to change its orientation to theleft or to the right so that a feel of the occupant being held thereincan be improved, but can alternatively be configured to cause the sideportions S22 of the seat back S2 to change their orientations to theleft or to the right so that the feel of the occupant being held thereincan be improved as well.

As in the first modified embodiment illustrated in FIG. 10, analternative configuration may be feasible in which the entire body ofthe seat back S2 is actuated by the actuator 51. For example, a pivotshaft 61 extending downward may be provided at a lower end of the seatback S2, and a bearing portion 62 which allows the pivot shaft 61 to bepivotally supported therein is provided at the seat cushion S1, so thatthe seat back S2 is provided in such a manner as to swivel to the leftand to the right relative to the seat cushion S1. Herein, posturecontrol mechanisms 50 (actuators 51) are provided at the left and rightsides of the rear portion of the seat cushion S1 so that the entire bodyof the seat back S2 can be actuated by causing the left and rightposture control mechanisms 50 to push appropriate locations of the seatback S2 frontward. With this alternative configuration as well, a goodhold of the occupant can be realized.

As in the second modified embodiment illustrated in FIG. 11, anotheralternative configuration may be feasible in which the entire body ofthe seat S is actuated by the actuator 51. For example, a mount 71 forsupporting the seat S is provided under the seat S, and a swivel table72 provided on the mount 71. The seat S is fixed on the swivel table 72.Herein, posture control mechanisms 50 (actuators 51) are provided at theleft and right sides of the rear portion of the mount 71 so that theentire body of the seat S can be actuated by causing the left and rightposture control mechanisms 50 to push appropriate locations of the seatcushion S1 frontward. With this alternative configuration as well, agood hold of the occupant can be realized.

In the above-described embodiment, the lateral acceleration is acquiredby computation based on the wheel velocity and the steering angle, butmay alternatively be acquired from a lateral acceleration sensor 94 asin the third modified embodiment illustrated in FIG. 12. The lateralacceleration and the steering velocity may be acquired, if an electroniccontrol unit provided in the car is available, by interrogating theelectronic control unit (ECU) 95 as in the fourth embodiment illustratedin FIG. 13.

In the above-described embodiment, an increase of the lateralacceleration due to a sharp-turn steering operation is predicted basedon the steering velocity and the lateral acceleration; however, thelateral acceleration due to the sharp-turn steering operation may bepredicted based not on the lateral acceleration but on the steeringvelocity.

In the above-described embodiments, the car seat apparatus 1 for use inan automobile is illustrated as an example of the vehicle seatapparatus, but the present invention is not limited thereto, and is alsoapplicable to any other vehicle seat apparatuses for use, for example,in snowmobile, ships and aircrafts, etc.

1-17. (canceled)
 18. A vehicle seat apparatus comprising: a seatincluding a seat cushion and a seat back; a posture control mechanismincluding left and right actuators capable of changing an orientation ofat least a portion of the seat; and a controller configured to controlthe actuators, wherein the controller includes: a posture control unitconfigured to exercise a seat posture control over the actuators basedon a steering operation of an occupant, wherein the posture controlmechanism is configured to cause one of the left and right actuators topush the seat back or the seat cushion frontward, thereby changing anorientation of at least an entire body of the seat back to a left or toa right.
 19. The vehicle seat apparatus according to claim 18, whereinthe posture control unit is configured to activate the left actuator ofthe posture control mechanism if a right-turn state occurs, and toactivate the right actuator of the posture control mechanism if aleft-turn state occurs.
 20. The vehicle seat apparatus according toclaim 18, wherein the posture control mechanism is configured to changean orientation of the entire body of the seat back to the left or to theright relative to the seat cushion.
 21. The vehicle seat apparatusaccording to claim 20, wherein the seat back includes a shaft; andwherein the seat cushion includes a bearing portion in which the shaftis rotatably supported, in such a manner that the seat back is capableof being caused to swivel to the left or to the right relative to theseat cushion on the shaft caused to rotate relative to the seat cushion.22. The vehicle seat apparatus according to claim 21, wherein the shaftis disposed between the left and right actuators.
 23. The vehicle seatapparatus according to claim 18, wherein the posture control mechanismis configured to change an orientation of the seat cushion.
 24. Thevehicle seat apparatus according to claim 23, wherein the posturecontrol mechanism includes a swivel table provided on a mount in amanner that permits the swivel table to swivel relative to the mount,and the seat is fixed on the swivel table.
 25. The vehicle seatapparatus according to claim 24, wherein the left and right actuatorsare disposed in positions rearward relative to the swivel table.
 26. Thevehicle seat apparatus according to claim 23, wherein the controller isconfigured to keep the orientation of the seat cushion fixed throughouta period of time during which a predetermined condition is satisfied.27. A vehicle seat apparatus comprising: a seat including a seat cushionand a seat back; a posture control mechanism including an actuatorcapable of changing an orientation of at least a portion of the seat;and a controller configured to control the actuator, wherein thecontroller includes: a posture control unit configured to exercise aseat posture control over the actuator based on a steering operation ofan occupant, wherein the posture control mechanism is configured tochange an orientation of at least an entire body of the seat back to aleft or to a right, wherein the controller includes: a lateralacceleration acquisition unit configured to acquire a lateralacceleration; and a steering velocity acquisition unit configured toacquire a steering velocity, wherein the posture control unit isconfigured: to activate the seat posture control when a magnitude of thelateral acceleration acquired by the lateral acceleration acquisitionunit becomes greater than a first acceleration threshold value, as wellas to activate the seat posture control on conditions that the steeringvelocity acquired by the steering velocity acquisition unit has amagnitude greater than a steering velocity threshold value and adirection of the lateral acceleration is opposite to a direction of thesteering velocity and when the magnitude of the lateral accelerationacquired by the lateral acceleration acquisition unit becomes greaterthan a second acceleration threshold value which is smaller than thefirst acceleration threshold value, wherein the posture control unit isconfigured to bring the seat posture control to an end when themagnitude of the lateral acceleration becomes smaller than a resetthreshold value during the seat posture control, and wherein a magnitudeof the second acceleration threshold value is smaller than the resetthreshold value.
 28. The vehicle seat apparatus according to claim 27,wherein the steering velocity threshold value is variable through anoperation of a user.